Identification of two integral glycosomal membrane proteins in Trypanosoma brucei

Glycosomal membranes of bloodstream form Trypanosoma brucei were purified to apparent homogeneity by sodium carbonate treatment and found to contain two major integral membrane proteins of 26 kDa (band 10) and 24 kDa (band 11). The procyclic-form glycosomal membranes isolated by the same procedure also resulted in a homogeneous preparation, but each piece of membrane thus purified was associated with an electron-dense granule. Procyclic membranes also contained primarily bands 10 and 11. These two proteins were selectively reduced by protease treatment of intact glycosomes, suggesting surface exposed domain(s) of the two proteins accessible to proteolytic digestion. They and band 8 protein also vanished in glycosomal lysates by apparent proteolysis, implying the presence of a specific protease which degrades the integral membrane proteins upon the loss of membrane integrity. The two proteins, hydrophobic in nature and apparently unglycosylated, have no known biological functions, but their possible involvement in translocating precursor proteins from the cytoplasm into the glycosome of T. brucei is postulated.